The invention relates to a preparation method of micron order spherical iron powder and belongs to the technical field of powder metallurgy. The method includes the steps that after super-pure iron ore concentrate powder is screened and dried, the super-pure iron ore concentrate powder and reducing gas containing methane are introduced into a conveying reactor, the super-pure iron ore concentratepowder is subjected to fast reducing in a high-temperature area of the conveying reactor, the reducing temperature is 1200-1600 DEG C, the reducing time is 1-50 s, and after reducing, iron-carbon molten drops are obtained; the iron-carbon molten drops are fast cooled when passing through a cooling area of the conveying reactor, and are solidified to form spherical iron-carbon alloy powder; the spherical iron-carbon alloy powder is collected; and the spherical iron-carbon alloy powder is fed into a fluidizing bed, the secondary fine reducing process is performed, and the micro order spherical iron powder with the metallization rate large than or equal to 99% is obtained. According to the method, the reaction time is shortened, operation is easy and convenient, and the micro order sphericaliron powder high in sphericity degree, low in oxygen content, narrow in product particle size distribution and not prone to oxidization is effectively prepared.